1. Field of the Invention
The invention relates to semiconductor wafer process systems and, more particularly, the invention relates to a method and apparatus for controlling contamination in a loadlock of a semiconductor wafer processing system.
2. Description of the Background Art
Semiconductor wafer processing systems comprise a loadlock wherein a plurality of wafers are stacked that are awaiting processing within a system. These wafers are removed from the loadlock one at a time by a robot and transported to various processing chambers within the system. Once processed, the wafers are returned from the process chambers to the wafer cassette in the loadlock for removal from the system.
During wafer processing within the system contaminants adsorb onto the wafers. Typically the reactant gases adsorb onto the wafer surface and when the wafer is returned to the loadlock the adsorbed material will desorb. The desorbed gases combine with moisture in the loadlock to form a corrosive film that coats the interior surfaces of the loadlock and the wafers. Such coating of the interior surfaces causes corrosion of the surfaces within the loadlock, and causes the formation of condensation particles upon the wafers. The surface corrosion creates tremendous quantities of corrosion byproduct particulates that disperse throughout the loadlock to contaminate the wafers.
Therefore, a need exists in the art for a method and apparatus that controls corrosive contaminants within a loadlock.
The disadvantages associated with the prior art are overcome by a method and apparatus that heats the atmosphere of a loadlock. Specifically, the apparatus heats the loadlock to inhibit the formation of corrosive byproduct particles. In addition, the apparatus may supply a purge gas to the loadlock to dilute and remove both moisture and corrosive gases from the loadlock. To provide, heat to the loadlock, at least one heater is attached to the walls of the loadlock to desorb the contaminants from the surfaces within the loadlock. These desorbed contaminants are exhausted from the loadlock by a vacuum pump or flushed from the loadlock by a flow of the purge gas. As such a combination of heating and purging effectively eliminates both the moisture and corrosive gases from the loadlock to eliminate a source of wafer contamination.